1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for requesting resumption of an extended real-time Polling Service (ertPS) in a broadband wireless communication system.
2. Description of the Related Art
Available radio resources are limited in a wireless communication system. Thus, a scheduling scheme that effectively uses the limited radio resources is required. Effective scheduling includes certain requirements such as the reallocation of necessary services by rapidly recollecting unnecessarily allocated resources, the deceasing of an amount of information exchanged using radio resources, and the allowing of residual resources to be used for other usages.
The wireless communication system defines a scheduling scheme according to a service property and type in order to ensure Quality of Service (QoS). Examples of the scheduling scheme include an Unsolicited Grant Service (UGS), a real-time Polling Service (rtPS), an extended real-time Polling Service (ertPS), etc.
The ertPS is an uplink resource allocation scheme and has the following characteristics. Resources are persistently allocated to a connection employing the ertPS at the request of a Mobile Station (MS). Unless there is a change in a requested resource amount, the MS transmits traffic using the allocated resources without additional polling. In other words, the same resources are persistently allocated to the MS without additional polling for the ertPS connection. Therefore, if a data rate needs to be decreased or increased, the MS transmits control information to a Base Station (BS) in order to report the increase or decrease of the required resource.
In addition to the increase or decrease of the required resource, the MS can request a temporary stop of uplink resource allocation. For example, a system using Voice over Internet Protocol (VoIP) has a talk-spurt period and a silence period. During the silence period, there is no data to be transmitted. As such, in the silence period having no data to be transmitted, the MS requests a temporary stop of resource allocation for the ertPS connection.
The ertPS connection whose resource allocation is temporarily stopped can be resumed according to the following methods. In a first method, the MS transmits a Bandwidth Request Header (BRH) including required resource amount information. In a second method, through a Channel Quality Indicator (CQI) channel, the MS transmits a Channel Quality Indicator CHannel (CQICH) codeword indicating an ertPS connection resumption request. Accordingly, the BS receives the CQICH codeword for the ertPS connection resumption request and then allocates uplink resources according to a maximum sustainable traffic rate of the ertPS connection of the MS. In general, the overhead generated in the second method is less than that generated in the first method. Therefore, the second method is prevalently used. The CQI channel is designed for channel information feedback of the MS, but may also be used to transmit the CQICH codeword used for a special purpose such as the ertPS connection resumption request, etc. In this case, the CQICH codeword used for the special purpose is determined according to a system configuration.
If only one CQICH codeword exists for the ertPS connection resumption request, it is difficult for an MS having a plurality of ertPS connections to use the method employing the CQICH codeword when the ertPS connection resumption is requested. This is because the BS which receives the CQICH codeword for the ertPS connection resumption request cannot identify a connection requested to be resumed among the plurality of ertPS connections. Accordingly, for a case of an MS having a plurality of ertPS connections, there is a need for a method of identifying the plurality of connections when ertPS connection resumption is requested.